Well, if you're truly all over the board--like a shotgun--it's a relatively easy fix.
GET WITH AN INSTRUCTOR. It may seem expensive and frivolous at first, but you'll save a grand in ammo and failed attempts to solve it on your own. An instructor can diagnose your shooting and help you solve it--in 10 minutes you'll know the problem and in an hour it'll be over.
If not, here are some things to look at/think about:
You either have an issue with using your sights--and that could mean that you're blinking or just not looking at them--or you have so much motion in your hold that you can't replicate a given shot.
Look solidly at the top center of your front sight in slow fire. You want equal light, equal height, target fuzzy. If the gun starts to move, take it down and BREATHE. Shoot your 6 shots as 6 one shot strings rather than one six shot string, breathe between shots, look at the clouds, whatever. Then settle in and do it again.
Resist the temptation to look over the gun to see where you hit the target. This will tend to make you shoot high (because you're looking before the shot breaks). Just disregard the results until your string is done, then go down and have a look.
Relax. Keep your arms relaxed from the shoulders to the wrists. If they are tense they will tend to wobble after 6-10 seconds (they want air). if you're relaxed you'll have MUCH more time before movement sets in. You can't fight recoil and win, so live with it. Let it happen--let the gun come up and settle back in naturally. If the gun stays pointed up in recoil, you're gripping too hard. Relax. If you feel like you should be on the cover of SWAT Monthly, you're trying too hard.
Breathing--that is great advice. A lot of new shooters hold their breath while they shoot. They start to run out of air and jerk the trigger when the sights are close--they rush the shot so they can breathe. Plan B? Breathe normally while you shoot.
Of course, this is for bullseye shooting. For Defensive shooting, we have a whole different set of parameters.
Dan